An electrophotographic image forming apparatus consists mainly of a unit provided with a photoconductive drum, a developing apparatus, a transfer apparatus, a heating (i.e., fixing) apparatus, and the like. Depending on a configuration of the image forming apparatus, a usage amount is previously set for each of these unit and apparatuses as replaceable parts. When these unit and apparatuses reaches the end of their remaining lives, they may be replaced. For example, a process cartridge provided with a photoconductive drum, a developing apparatus and the like is replaceable as a consumable supply. A transfer apparatus, a heating apparatus, a feed roller and the like may also be set to be replaceable as replaceable parts.
In an image forming apparatus, it is important to properly set a remaining live of a replaceable part, to inform a user that an end of the residual life is approaching based on a residual life prediction result (i.e., a prediction result of a usage amount) and to inform the user that the replaceable part has reached the end of the residual life.
A heating apparatus will be described as an exemplary replaceable part. As a heating apparatus for heating and fixing an image transferred to a recording material, there has been a configuration provided with a heat roller as a heating member maintained at a predetermined temperature and a pressure roller as a pressurizing member pressed against the heat roller. This configuration is called a heat roller system in which a recording material as a to-be-heated material is introduced in a nip portion formed by the heat roller and the pressure roller and conveyed in a nipped manner while being heated.
Other than the heat roller system, there is a configuration in which a heater as a heat source and a heat-resistant film (hereafter, referred to as a film) as a flexible endless belt that is conveyed while being disposed opposite to and pressed against the heater and a support (also referred to as a stay) of the heater are used. This configuration is further provided with a pressure roller as a pressurizing member that makes the recording material as a to-be-heated material be in close contact with the heater via the film. This configuration is called film heating system in which a non-fixed image formed and supported on a surface of the recording material is fixed by heat to the surface of the recording material by applying heat of the heater to the recording material via the film.
Whether such a heating apparatus has reached the end of its residual life can be determined by determining whether the number of sheets of the recording materials that have passed the heating apparatus, a cumulative value of driving time (i.e., rotation time) of the heating apparatus, and the like have become equal to or greater than previously set thresholds. As methods for accurately predicting a residual life of a heating apparatus, a method for cumulating a rotation time while weighting in accordance with a temperature of a heating apparatus (see PTL 1) and a method for cumulating the number of passed sheets while weighting in accordance with a passing state of a recording material (see PTL 2) have been proposed.